1. Field of the Invention
The present invention relates to a saddle-mounted type four-wheel vehicle constructed such that the engine output can be transmitted to the four front and rear wheels by means of a belt-type variable transmission. In more detail, it relates to a saddle-mounted type four-wheel vehicle wherein the frictional heat resulting from the operation of the belt-type variable transmission is removed by feeding cooling air from outside into the interior of this belt-type variable transmission.
2. Description of the Related Art
For example, as shown in documents such as Japanese Patent Publication No. 2843570, Japanese Patent Publication No. 2963052 and Japanese Laid-Open Patent Publication No. 2000-199463, saddle-mounted type four-wheel vehicles, wherein the four front and rear wheels are driven by variable transmission of engine output by means of a belt-type variable transmission, are known. In such systems, an induction box is fixed to a front cover that covers the front wheels and the top of the front of the vehicle frame. An inlet duct extending from this induction box is connected to a belt-type variable transmission, so as to prevent deterioration of the material of the belt by removing the frictional heat produced by operation of the belt-type variable transmission by feeding external air to the belt-type variable transmission as cooling air.
By connecting an inlet duct to the induction box provided on the front cover as described above, entry of foreign matter such as water, sand, mud or dust into the inlet duct can be effectively reduced and the resistance to air induction can be lowered by making the air current flowing into the inlet duct more uniform.
However, a change of the relative position of the induction box provided on the front cover with respect to the vehicle frame may result from factors such as running vibration or impacts. It has been noted that large relative changes in position between the belt-type variable transmission provided on the vehicle frame and the induction box provided on the front cover, causes separation of the inlet duct from the induction box or belt-type variable transmission. This may occur at the instant of a severe jolt to the vehicle due to running over objects or irregular terrain. Damage to the inlet duct may also occur. The same concerns also apply to the outlet duct through which cooling air that was fed into the belt-type variable transmission is evacuated.
In view of the problems described above, an object of the present invention is to reduce separation or damage to the inlet duct and outlet duct connected to the belt-type variable transmission and improve durability of the belt-type variable transmission. Other objects of the invention are to lower the air induction resistance, simplify the construction and improve the layout of the inlet duct by preventing induction of foreign matter such as water, mud, sand or dust into the inlet duct.
In order to achieve the aforementioned objects, a saddle-mounted type four-wheel vehicle according to the present invention includes a vehicle frame, left and right front wheels and rear wheels provided at the front and rear of the vehicle frame, an engine unit that includes an engine and belt-type variable transmission and is mounted on the vehicle frame between the front and rear wheels, a saddle-type seat provided at the top of the vehicle frame, a steering wheel provided in front of the seat, and a front cover that covers the front wheels and the upper front part of the vehicle frame. The upper front part of the vehicle frame extends to approximately above the front wheel axle shaft. An induction box is provided between the upper front part of the vehicle frame and the front cover. This induction box is fixed to the vehicle frame and includes a cooling air induction port provided in the upper face thereof adjacent to the bottom face of the front cover. A duct linkage port provided in the bottom face of the induction box and an air induction port provided in the belt-type variable transmission are connected by an inlet duct. A positioning element is formed on a portion of this inlet duct, in order to position the portion with respect to structural members of the vehicle frame. An outlet duct is connected with a discharge port provided in the belt-type variable transmission, and a cooling air discharge port is provided at the downstream end of this outlet duct.
With such a construction, separation of the inlet duct from the induction box or belt-type variable transmission, or damage thereto, can be prevented and it becomes difficult for foreign matter such as water, mud, sand or dust raised by the front wheels to be sucked into the inlet duct within the front cover during running of the saddle-mounted type four-wheel vehicle. Furthermore, the construction related to fixing of the inlet duct is simplified.
Also, with the saddle-mounted type four-wheel vehicle according to the present invention, the portion of the inlet duct at which the positioning element is formed may be a middle portion of the inlet duct. The positioning element may include a fitting hook that fits tightly on the surface of an upright portion constituting the front part of the vehicle frame, and a bottom face of the fitting hook that contacts a transverse portion that is joined to the upright portion. In this way, movement of the inlet duct with respect to the vehicle frame is restrained and separation of or damage to the inlet duct is more reliably prevented. It should be noted that the fitting hook can be of very simple construction.
Furthermore, with the saddle-mounted type four-wheel vehicle according to the present invention a heat exchanger of the engine unit is provided near the front of the vehicle frame, a cooling fan for cooling the engine unit is provided behind the heat exchanger, and the inlet duct is extended downwardly and rearwardly to pass between the heat exchanger and cooling fan and below the cooling fan, and is connected to the air induction port of the belt-type variable transmission. In this way, air induction resistance is reduced by reducing bending of the inlet duct to a minimum and the layout of the inlet duct is improved.
Also, with the saddle-mounted type four-wheel vehicle according to the present invention, the cooling air induction port of the induction box is arranged at a higher position than the cooling air discharge port of the outlet duct. The cooling air discharge port is at a lower position than the highest part of the outlet duct, and the cooling air discharge port is arranged on the front face side of the outlet duct. In this way, on entering or leaving a deep-water channel at a comparatively steep angle, penetration of water from the cooling air induction port of the induction box, or from the cooling air discharge port of the outlet duct, is prevented.
Also, with the saddle-mounted type four-wheel vehicle according to the present invention, another positioning element may be formed in a portion of the outlet duct in order to position the portion of the outlet duct with respect to the vehicle frame structural members. In this way, movement of the outlet duct with respect to the vehicle frame is restrained and separation of or damage to the outlet duct is reliably prevented.
Further, with the saddle-mounted type four-wheel vehicle according to the present invention, the portion of the outlet duct at which the positioning element is formed may be a middle portion of the outlet duct. The positioning element for the outlet duct may include a fitting hook that fits tightly on a cross member extending in the width direction and constituting part of the vehicle frame, an abutment portion that abuts on the side face of a structural member of the vehicle frame, and an engagement part that engages a corner formed by the side face and bottom face of an article accommodating box arranged below the seat. Since the fitting hook, abutment part and engagement part can be made of straightforward shape, while maintaining a straightforward construction of the outlet duct, positioning of the outlet duct can be reliably achieved while preventing separation thereof or damage thereto.
Also, with the saddle-mounted type four-wheel vehicle according to the present invention, a forwardly descending portion is formed at the upper front part of the vehicle frame, the induction box is arranged above this forwardly descending portion, and includes a chamber portion formed at the front of the induction box such that the bottom face of the chamber portion extends downwards with a shape substantially corresponding to the shape of the forwardly descending portion. A water discharge hole is provided at the lowest part of this chamber portion. In this way, a large induction box capacity can be ensured, lowering the air induction resistance and enabling moisture that has penetrated into the induction box to escape effectively.
Also, with the saddle-mounted type four-wheel vehicle according to the present invention, the upstream part of the inlet duct projects into the interior of the induction box through the duct linkage port, and bends in a direction away from the cooling air induction port within the induction box. The opening thereof is positioned higher than the bottom face of the induction box. In this way, even if water penetrates into the induction box from the cooling air induction aperture, it is difficult for this water to be sucked into the inlet duct.
Further, with the saddle-mounted type four-wheel vehicle according to the present invention, screening plates extend from the upper face of the induction box and surround the cooling air induction port of the induction box. An air intake guide protrudes above the front cover and a cooling air intake port is formed in front of this air intake guide. The screening plates project within the protruding shape of the air intake guide. In this way, foreign matter such as water, mud, sand or dust that has been raised by the front wheels within the front cover during running cannot easily enter the cooling air induction port of the induction box, since it is obstructed by the screening plate.
Also, with the saddle-mounted type four-wheel vehicle according to the present invention, the bottom face of the induction box is inclined, the cooling air induction port being positioned above the lowest part of this inclination. A guide cylinder surrounding the cooling air induction port extends within the induction box, extending towards the lowest part of the inclined bottom face of the induction box. In this way, once air that has been sucked in from the cooling air induction port has flowed to the bottom of the induction box, it flows into the inlet duct that opens thereabove, so that foreign matter (in particular moisture) contained in the inducted air is separated from the air current and is not easily sucked into the inlet duct.
Also, with the saddle-mounted type four-wheel vehicle according to the present invention, the screening plate positioned at the front edge of the cooling air induction port is a perforated plate. In this way, entry of foreign matter into the cooling air induction port can be prevented and the air induction resistance can be lowered.
Furthermore, with the saddle-mounted type four-wheel vehicle according to the present invention, a gap is provided between the tips of said screening plates and said air intake guide. In this way, there is no possibility of mutual contact of the screening plate and the air intake guide during running, so generation of abnormal noise and/or damage can be prevented.
In order achieve the aforementioned objects, an air cooling system for a vehicle transmission according to the present invention includes an induction box fixed to a vehicle frame and including a cooling air induction port provided in the upper face thereof. A duct linkage port provided in the bottom face of the induction box and an air induction port provided in the vehicle transmission are connected by an inlet duct. A positioning element is formed on a portion of this inlet duct, in order to position the portion with respect to structural members of the vehicle frame. An outlet duct is connected with a discharge port provided in the vehicle transmission, and a cooling air discharge port is provided at the downstream end of this outlet duct.
In order achieve the aforementioned objects, an air cooling system for a vehicle transmission according to the present invention includes an induction box provided between an upper front part of a vehicle frame and a vehicle front cover. The induction box is fixed to the vehicle frame and includes a cooling air induction port in an upper face thereof adjacent to a bottom face of the front cover. The induction box further includes a duct linkage port in a bottom face thereof for connection of an inlet duct thereto.